This is important. People seem to get the wrong idea about long critiques once in a while. It's not an attack or an insult; it's just me trying to help you improve. While I'm not trying to sound rude, I definitely will not sugar-coat anything for you. If it looks really ugly, I'm going to say it looks really ugly (and explain why). Likewise, if it looks pretty, I'll tell you it looks pretty (and explain why). I won't make up nice/mean things to say about your screenshot to make you happy/angry. The purpose of a critique is to help you improve and is, in absolutely no way, written malicious intent.

I like the idea of windows on the ceiling. Skylights are for rich folk, it shows the person had some large sums of money. However rich people are not stupid. No one would put a window shaped like that on their ceiling; they'll use something to compliment the shape of the inside of their building (I'll comment on your architecture later). Here is a plethora of examples I found. Yours doesn't compliment the shape of the ceiling at all (I would suggest a rectangular shape instead) and it looks completely inappropriate. Your window has a clear "up" side (top of the arch). By putting it on the ceiling, you make people's brains do this.

Aside from that, those window models are terribly stretched to the point where you might as well be using an engine from the days of Atari. What are they at, like 7x the size of their normal model? At most, I'd say 2 is the limit for stretching things. After that, they start looking weird... really really weird. Seriously man, don't do that.

Another thing about the windows, why is there a great big grey fogbox clipping through them? I can clearly see it inside your map on the ceiling; no idea why you didn't notice that yourself. If you did, you should have moved it because it looks awful and that's not how fog does things. Place it above the windows or lower it enough that the change is gradual. The light coming from the window is also god-awful. It doesn't spread evenly, there's no clear sign that it's even coming directly from the windows (if you have fog, you have no excuse for not using billboards). The lights in general have been placed very poorly with oddly-chosen colours (brightest ones should be near the windows, a dimmer one with a larger radius should be placed further away, spotlight should be the brightest of all three, boxlight should be the dimmest of all three and reflect the general colour of the room). I'm not even sure you have a boxlight. Let me attempt to make this clear: unless you have a damn good reason (and can pull it off well), you should always have a boxlight Amnesia's Storage Room, anyone?

Nextly, those clear windows on the inside of your map. For the love of all that is good and holy, why would you have so many windows? It looks extremely repetitive and boring. Break them up with some normal wall pieces in between or put some details on the other side of them. Right now, they make absolutely no sense. Usually, windows like that are designed to let light in to rooms that are in the middle of a building or so the people inside the room observe what's outside/people outside can observe inside. These kinds of windows are also a very modern thing. Amnesia assets don't lend themselves to modern.

I've made four paragraphs on just the windows. That should tell you how much is wrong with them.

The architecture of the area makes no bloody sense. You have a set of walls made of stone, followed by a set of walls made of wood, followed by another set of walls made of stone. Those stone walls would completely crush the wooden walls and destroy your entire structure. Not to mention, they don't flow together coherently. You can get away with using random assets together (take a look at some of ALITD's stuff in Robosprog's timelapse), but they still have to make sense. Your map does not make sense. There are also ceiling pieces clipping together at corners. Victor, buddy, there are corner ceilings in the assets. They're not hard to find at all. Utilize them. There needs to be pillars to support the upper floors of the building as well (since you have them coming in a bit towards the center).

If that's not weird enough, the sheer scale of your area should be an area of concern. Glass is heavy and would need something to support it (oh look, another problem with the windows being so gigantic). Not to mention that, the larger a room is, the harder it is to detail. I've yet to see anything detailed you in any sense of the word, so I would suggest sticking to smaller rooms until you've mastered the basics of detailing.

I'm not even going to comment on detailing because there is none. It doesn't just need to be stuff on the walls, it needs to be dust in the air, cobwebs on the ceiling, bits of glass/rocks/wood on the floor from the shattered window, water stains where the building's been affected by its expose to the elements. Most of all, however, this hallway/room needs a reason to be this huge. Unless you plan on having a herd of apatosauruses waltz through the hallways on their hind legs, I don't see any logic behind the size of this area.

To add another note about lighting and such things, a bit of colour theory would do you some good.